Humans with injury to the central nervous system (e.g., brain and spinal cord) can suffer from chronic central neuropathic pain. However, standard analgesics, such as nonsteroidal anti-inflammatory drugs, opioids, tricyclic antidepressants, anticonvulsants and antispasmodics, are ineffective in relieving the chronic central neuropathic pain, in particular pain associated with spinal cord injury. Further, relief of pain by certain analgesics can result in adverse side effects such as fatigue, confusion, dizziness, somnolence and speech difficulty thereby diminishing the attractiveness of the analgesic to the human. Thus, there is a need to develop new, improved and effective methods of treatments for pain in humans with central nervous system injury which alleviate pain without adverse side effects.